Medically Assisted Reproduction and Risk of Cancer Among Offspring

Key Points Question Does cancer risk differ among children born after fresh embryo transfer (ET), frozen embryo transfer (FET), or artificial insemination (AI) and children conceived naturally? Findings In this cohort study of 8 526 306 children, the overall risk of cancer did not differ among children born after fresh ET, FET, or AI and children conceived naturally. However, an increased risk of leukemia was observed among children born after fresh ET (especially those with the longest follow-up) and among children born after FET (particularly acute lymphoblastic leukemia). Meaning These findings suggest that the risk of leukemia among children conceived by FET or fresh ET should be further monitored.


Introduction
Childhood cancer is a leading cause of death among children worldwide.Overall, 1800 cases occur every year in France among children aged younger than 15 years, with half occurring before age 6 years. 1 The early onset after birth and the embryologic characteristics of some cancers 2 suggest that the causes may take place around conception.[6] Children born after MAR represent a growing population worldwide. 7Compared with children conceived naturally, children born after MAR have an increased risk of adverse perinatal outcomes, including preterm birth, low birth weight, and fetal growth anomalies. 8,9However, little is known about the medium-term and long-term effects of fertility treatments on child health.Previous studies on the risk of childhood cancer among children born after ART, most of which were based on relatively small cohorts of exposed children [10][11][12][13][14][15][16][17][18] or interview-based case-control study designs, [19][20][21][22][23][24] provided contrasting results.With regard to findings from large cohorts including 100 000 or more exposed children, [25][26][27][28][29] no increase in overall cancer risk has been reported, except 1 study 29 that reported a marginal association with ART.6][27][28][29] In addition, previous studies that assessed the risk of childhood cancer by fresh ET or FET 12,15,17,[25][26][27][28] were based on limited numbers of case patients exposed to each ART modality.
We aimed to assess the risk of cancer, overall and by cancer type, among children born after ART use (fresh ET or FET) or after AI compared with children conceived naturally, considering all children born in France between 2010 and 2021.

Methods
This cohort study was authorized by decree 2016-1871 from December 26, 2016, relating to the processing of personal data from the National Health Data System and French law Art.1461-13 and 14.
The EPI-PHARE Scientific Interest Group in Epidemiology of Health Products, which has permanent regulatory access to the data from the French National Health Data System (SNDS; in application of the provisions of Art.R. 1461-12 et seq.9 of the French Public Health Code and French Data Protection Authority decision CNIL-2016-10 316), was exempted from participant consent and institutional review board approval.The study was registered in the EPI-PHARE SNDS-based registry under reference T-2020-10-272.The study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.

Data Source
This study was conducted using comprehensive data from the French National Mother-Child Register (EPI-MERES) for all children born alive in France between January 1, 2010, and December 31, 2021.
The EPI-MERES database was built from the SNDS, 30 which provides comprehensive hospitalization and health insurance reimbursement data for more than 99% of the French population; it is an unselected register of all pregnancies from 2010 onward in France, identified by end-of-pregnancy diagnoses and procedure codes and linked to their offspring using a deterministic algorithm.Linkage of mother and infant records is available for 95% of children.As of today, the EPI-MERES includes data for more than 8.5 million liveborn children, accounting for 98% of all live births recorded in France since 2010.The EPI-MERES contains a wide set of information on mothers (medical history and sociodemographic characteristics), pregnancies (start and end dates, mode of delivery, and pregnancy outcome), and offspring (gestational age and birth weight, outpatient and inpatient health care use, and hospital discharge diagnoses and medical procedures coded according to the

Classification Commune des Actes Médicaux [CCAM]
). Patients with long-term diseases (LTDs), such as cancer, benefit from full coverage of their health expenditure, and the diagnosis is recorded in the Datamart Consommation Inter Régime (DCIR) using International Statistical Classification of Diseases, Tenth Revision (ICD-10) codes.The DCIR is a French health care expenditure database that contains all of the individual data of health insurance beneficiaries.[33][34]

Exposure Assessment
Artificial insemination and ART are fully covered by French health insurance after medical validation and until a maternal age of 43 years.Procedures related to MAR and their dates were identified using CCAM codes for oocyte retrieval, ET, and AI (eTable 1 in Supplement 1).Children were considered as born after MAR when the conception date fell within 21 days of the MAR procedure recorded in the SNDS, and as naturally conceived otherwise.The recorded date of ET was retained as the ART procedure date.Children were considered as born after fresh ET when there were fewer than 21 days between the date of oocyte retrieval and the ET, and as born after FET when the delay was 21 days or longer.

Childhood Cancer
Childhood cancers were identified using hospital discharge and LTD diagnoses, using algorithms constructed in collaboration with experts in cancer coding from the French National Registry of Childhood Cancers (RNCE).Children were considered case patients with cancer if they met at least 1 of the following criteria: (1) had at least 2 hospitalizations with a discharge diagnosis of cancer; (2)   had at least 1 hospitalization with a discharge diagnosis of cancer in addition to 1 hospitalization for oncologic treatment (chemotherapy, radiotherapy, oncologic surgery, or bone marrow transplantation) or an LTD diagnosis of childhood cancer; or (3) had 1 hospitalization with a discharge diagnosis of cancer, followed by death within 6 months.
Cancer diagnoses were categorized into 12 groups as close as possible to those of the International Classification of Childhood Cancer, Third Edition (ICCC-3; eTable 2 in Supplement 1), 35 using ICD-10 codes, in the absence of the morphology and topography codes of the International Classification of Diseases for Oncology, Third Edition (ICD-O-3) required for ICCC-3.For each child, the most frequently coded cancer diagnostic group among all their hospital stays was retained as the cancer diagnosis.Because of a lack of specificity, for malignant bone tumors and gonadic neoplasms, only case patients with identification of an oncologic treatment were retained.Because information available in the SNDS does not allow for the proper individual identification of same-sex siblings born of multiple pregnancies, only 1 case patient was retained in the case of identical cancer diagnosis in same-sex twins.Anonymized data provided by the RNCE for children born and diagnosed in the 2010 to 2015 period were used as the reference set for the distribution in large categories of cancer diagnoses (eTable 3 in Supplement 1).

Covariates
Characteristics of children included year of birth, sex, singleton or multiple birth, birth weight (<1000, 1000-2499, 2500-3999, or Ն4000 g), gestational length (Յ28, 29-32, 33-36, 37-41, or Ն42 weeks), and an indicator of fetal growth (small, adequate, or large for gestational age).Major congenital malformations were identified based on hospital discharge diagnoses within up to 12 months after birth, based on ICD-10 codes selected by the European Surveillance of Congenital Anomalies network. 36Characteristics of mothers included maternal age at the index child birth (Յ24, 25-29, 30-34, 35-39, or Ն40 years) and the French census-based deprivation index 37 of the municipality of residence at birth, used as a proxy for the household socioeconomic category.The French census-based deprivation index is categorized in quintiles, with the fifth quintile representing the most deprived municipalities.

Statistical Analysis
Children contributed to person-years at risk from their date of birth until the date of first hospitalization with a discharge diagnosis of cancer, the date of death, or the end of the study on June 30, 2022, whichever occurred first.We compared the risk of cancer among children born after fresh ET, FET, or AI with that of children conceived naturally, taking all cancers together and by main cancer groups.The risk of leukemia was examined overall and by leukemia subtype (acute lymphoblastic leukemia [ALL] and acute myeloid leukemia [AML]).
Adjusted hazard ratios (HRs) and 95% CIs were estimated using Cox proportional hazards regression models including a priori selected covariates reported to be associated with childhood cancers and MAR in the literature (ie, sex, year of birth, multiple birth, maternal age at childbirth, and deprivation index).Additional models also adjusted for potential mediating factors including gestational length, birth weight, macrosomia, and congenital malformations.The percentages of missing data were small.To assess cancer risk among children followed over a longer period, complementary analyses restricted to children born between 2010 and 2015 were performed for most frequent childhood cancers.Partial likelihood tests were performed post hoc to determine whether the estimated HR differed across the various MAR modalities.Sensitivity analyses restricted to singletons were performed.Additional sensitivity analyses were performed using the first coded (instead of the most frequently coded) diagnosis group as the cancer diagnosis and restricting the case definition to children with chemotherapy exposure.The proportional hazards assumption was tested with Schoenfeld residuals, and there were no clear violations.Hazard ratios were not estimated for categories with fewer than 5 case patients.All P values were 2-sided and a significance level of .05 was applied.Data analysis was performed from December 1, 2021, to June 30, 2023, using SAS, version 9.4 (SAS Institute Inc).

Characteristics of the Study Population
The study cohort included 8 526 306 children, with a mean (SD) age of 6.4 (3.4) years.Boys comprised 51.2% of the cohort, and girls comprised 48.8%; 96.4% of children were singletons, 12.1% were small for gestational age at birth, and 3.1% had a congenital malformation.There were 260 236 children (3.1%) born after MAR, including 133 965 (1.6%) after fresh ET, 66 165 (0.8%) after FET, and 60 106 (0.7%) after AI.Although the number of births after fresh ET decreased from 2015 onward, a continuous increase in the number of children born after FET was observed over the study period and FET started to prevail over fresh ET in 2020.The annual number of children born after AI remained stable over the study period (Figure).Frozen embryo transfer

Artificial insemination
Compared with children conceived naturally, children born after MAR were more often part of a multiple birth, had lower birth weight and gestational age, were more often born small for gestational age, and were more often diagnosed with a congenital malformation.Children born after FET were more frequently born large for gestational age.Mothers whose children were born after MAR were older and their residence at birth was more often in the least deprived municipalities (Table 1).
Cancer Risk Among Children Born After Fresh ET, FET, or AI  2).
In the analyses restricted to children born between 2010 and 2015, the median follow-up duration was longer and more homogeneous for the different modes of conception.These median durations were as follows: 9.4 (IQR, 7.8-10.9)years for natural conception, 9.4 (IQR, 7.9-10.9)years for fresh ET, 8.8 (IQR, 7.5-10.4)years for FET, and 9.3 (IQR, 7.9-10.Additional adjustments for birth characteristics and congenital malformations marginally modified the estimates (eTables 5-7 in Supplement 1).Results remained stable in sensitivity analyses restricted to singletons or based on alternative case definitions (eTables 8-10 in Supplement 1).

JAMA Network Open | Pediatrics
Medically Assisted Reproduction and Risk of Cancer Among Offspring

Discussion
In this nationwide birth cohort study including more than 8.5 million children, the risk of any cancer was not increased among children born after MAR.However, the findings suggest that children born after fresh ET or FET had a higher risk of leukemia.
6][27][28] However, the grouping of all cancer types, although meaningful for detecting common risk factors, could miss subtype specificities.In line with our findings, 4 previous studies 13,17,27,28 reported an increased risk of leukemia among children born after ART.With regard to ART modalities such as fresh ET or FET, the literature is still sparse and results are conflicting.The data used in this study were obtained from one of the largest cohorts of children after FET to date; thus, our results support the hypothesis of an increased risk of leukemia, mainly observable for ALL, with a limited number for AML.In our complementary analysis restricted to births between 2010 and 2015, the risk of leukemia was increased for children born after FET (although statistical significance was not reached because of reduced numbers of exposed case patients) and also for those born after fresh ET, probably as a result of more homogeneous follow-up between children born after fresh ET or FET and better coverage of the age range corresponding to the incidence peak of leukemia (2-6 years).Sargisian et al 28 39,40 This finding is also supported by studies that suggest an association between MAR-related procedures and imprinting disorders, 41 such as Beckwith-Weidemann syndrome, 42 a pediatric overgrowth disorder involving a predisposition to tumor development.

Strengths and Limitations
Our study has major strengths.diagnoses.Conversely, the number of bone tumors, hepatic tumors, and malignant CNS tumors was higher than that of the registry, possibly reflecting inclusions of metastatic localizations as primary sites.Exposure or outcome misclassification might have attenuated the associations.
Additionally, information on child emigration was not available.Given the rarity of childhood cancers, the number of potential undetected cases because of child emigration is likely to be small.
Child emigration could also lead to overestimation of the follow-up time.However, these potential misclassification biases might not differ by conception mode; therefore, they should not have substantially biased our estimates.
Many potential confounders have been taken into account.However, as with most studies on the effects of fertility treatments on child health, our study was unable to distinguish between possible treatment effects and parental conditions underlying infertility 43 that might be associated with an increased risk of cancer in offspring.Therefore, residual confounding cannot be completely ruled out.
Finally, although this study included a large nationwide cohort, the absolute number of children with cancer was relatively small.Risk assessment of childhood cancers is challenging given their rarity, and results based on small numbers may be subject to both lack of power or the potential for spurious associations.We did not adjust for multiple comparisons.Therefore, these findings must be interpreted with caution.

Conclusions
In this cohort study, the overall risk of cancer was not increased after MAR but our findings suggest that children born after FET or fresh ET may have an increased risk of leukemia.This risk, although resulting in a limited number of cases, needs to be monitored in view of the continuous increase in the use of ART.

Figure .
Figure.Children Born in France Between 2010 and 2021 After Medically Assisted Reproduction Abbreviations: AI, artificial insemination; ALL, acute lymphoblastic leukemia; AML, acute myeloid leukemia; CNS, central nervous system; ET, embryo transfer; FET, frozen embryo transfer; HR, hazard ratio; IR, incidence rate per million person-years; MAR, medically assisted reproduction; NA, not applicable; RD, risk difference per million person-years.a Estimates are not provided when there were fewer than 5 exposed case patients.The number of person-years was 54 568 974 for children conceived naturally and 903 708, 331 770, and 391 001 for children conceived via fresh ET, FET, and AI, respectively.
8) years for AI.The risk of leukemia was significantly increased among children born after fresh ET (HR, 1.42 [95% CI, 1.06 to 1.92]; other association was observed (Table3).

Table 1 .
Perinatal Characteristics of Children Born in France Between 2010 and 2021, According to Mode of Conception a Abbreviations: AI, artificial insemination; ET, embryo transfer; FET, frozen embryo transfer; MAR, medically assisted reproduction; Q, quintile.a Unless indicated otherwise, values are expressed as No. (%) of children.

Table 2 .
Risk of Cancer Among Children Born in France Between 2010 and 2021 After Fresh ET, FET, or AI Compared With Children Conceived Naturally a

Table 3 .
Risk of Cancer Among Children Born in France Between 2010 and 2015 After Fresh ET, FET, and AI Compared With Children Conceived Naturally a provided when there were fewer than 5 exposed case patients.The number of person-years was 40 434 932 for children conceived naturally and 672 874, 183 818, and 284 868 for children conceived via fresh ET, FET, and AI, respectively.
Abbreviations: AI, artificial insemination; ALL, acute lymphoblastic leukemia; AML, acute myeloid leukemia; CNS, central nervous system; ET, embryo transfer; FET, frozen embryo transfer; HR, hazard ratio; IR, incidence rate per million person-years; MAR, medically assisted reproduction; NA, not applicable; RD, risk difference per million person-years.a Estimates are not b Adjusted for year of birth, sex, multiple birth, maternal age, and deprivation index.c Includes tumors of adrenal glands, peripheral nerves, and autonomic nervous system.
38nducted a study (median follow-up of 9.9 years) in Nordic countries, and they found an increased risk of leukemia among children born after FET vs children conceived naturally (HR, 2.22 [95% CI, 1.47 to 3.35]) but not among those born after fresh ET.In another study, Weng et al17found that the risk of leukemia was significantly increased among children born after fresh ET, but not among children born after FET.However, estimates were based on fewer than 5 exposed case patients by ART modality.A meta-analysis conducted by Zhang et al38reported no increased cancer risk among children born after ART based on 15 cohorts, but the authors found an increased risk of childhood cancer among children born after FET (pooled HR, 1.37 [95% CI, 1.04 to 1.81]) compared with children conceived naturally.However, the finding was not statistically significant when children born after fresh ET were most frequent childhood cancer groups and by MAR modality, and we had reliable individual information on major confounders and potential mediating factors.Our findings must be interpreted in light of some limitations.We used reimbursement and hospitalization data to identify exposure to MAR procedures and childhood cancer occurrence.With regard to exposure assessment, MAR-related procedures are expensive treatments that benefit from full insurance coverage in France; therefore, they typically are not subject to nondeclaration.Compared with reported numbers from the French Agency of over the same period, our study was able to identify more than 90% of liveborn children conceived by MAR, and the distribution by fresh ET, FET, or AI was comparable (eTable 11 in Supplement 1).Still, information on the type of ART (ie, ICSI) or cross-border fertility care was not available.With regard to outcome assessment, most pediatric cancers are life-threatening pathologies requiring hospitalization for diagnosis and treatment and are very unlikely to be underdiagnosed in France.The algorithms used in our study were able to identify the most frequent groups of childhood cancers with numbers close to that of the RNCE except for tumors of the adrenal glands, peripheral nerves, and autonomic nervous system, which were underestimated in our study based on ICD-10 It is based on one of the largest cohorts published to date and on comprehensive data covering the entire French population, and we used reliable and systematically collected data, with no potential for recall bias and selection bias.We performed analyses for the JAMA Network Open | Pediatrics JAMA Network Open.2024;7(5):e249429.doi:10.1001/jamanetworkopen.2024.9429(Reprinted) May 2, 2024 9/13 Downloaded from jamanetwork.comby guest on 05/04/2024 List of Codes Used for Identification of Medically Assisted Reproduction-Related Procedures eTable 2. Grouping of ICD-10 Diagnostic Codes Used to Approximate the International Childhood Cancer Classification eTable 3. Number of Cancers Among Children Born and Diagnosed in France Between 2010 and 2015 in the French National Registry of Childhood Cancers (RNCE) and in the Present Study eTable 4. Birth Characteristics of Children Born in France in 2010 to 2021 by Cancer Status eTable 5. Risk of Cancer in Children Born in France in 2010 to 2021 After Fresh Embryo Transfer Compared to Naturally Conceived Children eTable 6. Risk of Cancer in Children Born in France in 2010 to 2021 After Frozen Embryo Transfer Compared to Naturally Conceived Children eTable 7. Risk of Cancer in Children Born in France in 2010 to 2021 After Artificial Insemination Compared to Naturally Conceived Children eTable 8. Number of Cases, Incidence Rate, and Risk of Cancer in Children Born After Natural Conception, Fresh Embryo Transfer, Frozen Embryo Transfer, or Artificial Insemination in Singletons Born in France in 2010 to 2021 eTable 9. Risk of Cancer in Children Born in France in 2010 to 2021 After Fresh Embryo Transfer, Frozen Embryo Transfer, or Artificial Insemination Compared to Naturally Conceived Children eTable 10.Risk of Cancer in Children Born in France in 2010 to 2021 After Fresh Embryo Transfer, Frozen Embryo Transfer, or Artificial Insemination Compared to Naturally Conceived Children eTable 11.Number of Children Born After Medically Assisted Reproduction in France Between 2010 and 2020 According to the French National Agency of Biomedicine (ABM) and in the Present Study